Generally, cancer results from the deregulation of the normal processes that control cell division, differentiation and apoptotic cell death. Apoptosis (programmed cell death) plays essential roles in embryonic development and pathogenesis of various diseases, such as degenerative neuronal diseases, cardiovascular diseases and cancer. One of the most commonly studied pathways, which involves kinase regulation of apoptosis, is cellular signaling from growth factor receptors at the cell surface to the nucleus (Crews and Erikson, Cell, 74:215-17, 1993).
Nucleosides are glycosylamines consisting of a nucleobase (often referred to as simply base) bound to a ribose or deoxyribose sugar via a beta-glycosidic linkage. Examples of nucleosides include cytidine, uridine, adenosine, guanosine, thymidine and inosine.
Nucleosides can be phosphorylated by specific kinases in the cell on the sugar's primary alcohol group (—CH2—OH), producing nucleotides, which are the molecular building-blocks of DNA and RNA.
Nucleosides can be produced by de novo synthesis pathways, in particular in the liver, but they are more abundantly supplied via ingestion and digestion of nucleic acids in the diet, whereby nucleotidases break down nucleotides (such as the thymine nucleotide) into nucleosides (such as thymidine) and phosphate. The nucleosides, in turn, are subsequently broken down in the lumen of the digestive system by nucleosidases into nucleobases and ribose or deoxyribose.
In addition, nucleotides can be broken down inside the cell into nitrogenous bases, and ribose-1-phosphate or deoxyribose-1-phosphate.
In medicine several nucleoside analogues are used as antiviral or anticancer agents. The viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides, they are administered as nucleosides since charged nucleotides cannot easily cross cell membranes.
Mitogen-activated protein (MAP) Kinase/extracellular signal-regulated kinase (ERK) kinase (hereinafter referred to as MEK) is known to be involved in the regulation of numerous cellular processes. The Raf family (B-Raf, C-Raf etc.) activates the MEK family (MEK-1, MEK-2 etc.) and the MEK family activates the ERK family (ERK-1 and ERK-2). Broadly, the signaling activity of the RAF/MEK/ERK pathway controls mRNA translation. This includes genes related to the cell cycle. Hence, hyperactivation of this pathway can lead to uncontrolled cell proliferation. Deregulation of the RAF/MEK/ERK pathway by ERK hyperactivation is seen in approximately 30% of all human malignancies (Allen, L F, et al., Semin. Oncol. 2003. 30(5 Suppl 16):105-16). RAS, which can signal through both the PI3K/AKT and RAF/MEK/ERK, has a mutated oncogenic protein in 15% of all cancers (Davies, H. et al. Nature. 2002. 417:949-54). Also, activating BRAF mutations have been identified at a high frequency in specific tumor types (e.g., melanomas) (Davies, H. et al. Nature. 2002. 417:949-54). Although activating mutations in MEK itself don't appear to frequently occur in human cancers, MEK is thought to be an important drug target for treating human cancer because of its central role in the ERK pathway. Further, MEK inhibitory activity effectively induces inhibition of ERK1/2 activity and suppression of cell proliferation (The Journal of Biological Chemistry, vol. 276, No. 4, pp. 2686-2692, 2001), and the compound is expected to show effects on diseases caused by undesirable cell proliferation, such as tumor genesis and/or cancer.
It would be useful to provide a improved therapy which provides more effective and/or enhanced treatment of an individual suffering the effects of cancer.